CBSE Class 11 Chemistry Redox Reactions MCQs Set B

Question: Which of the following transition metal has zero oxidation state ?
a) [Fe(CO)₅]
b) NH₂.NH₂
c) NOClO₄
d) CrO₅
Answer: a

Question: In the following reaction 4P + 3KOH+ 3H₂O→3KH₂PO₂ + PH₃ 
a) phosphorus is both oxidised and reduced.
b) only phosphorus is reduced.
c) phosphorus is not oxidised
d) None of the options
Answer: a

Question: A mixture of potassium chlorate, oxalic acid and sulphuric acid is heated. During the reaction which element undergoes maximum change in the oxidation number?
a) S
b) H
c) Cl
d) C
Answer: c

Question: What is the oxidation number of elements in the free or in the uncombined state ?
a) +1
b) 0
c) +2
d) –1
Answer: b

Question: In the reaction given below, identify the species undergoing redox reaction 2Na_(s) + H_2(g) → 2NaH_(s)
a) Na is reduced and hydrogen is oxidised
b) Na is oxidised and hydrogen is reduced
c) Na undergoes oxidation and hydrogen undergoesreduction 
d) Both Na is oxidised and hydrogen is reduced and Na undergoes oxidation and hydrogen undergoesreduction 
Answer: d

Question: In oxygen difluoride, the oxidation number of oxygen is
a) – 2
b) – 1
c) + 2
d) +1, – 2
Answer: c

Question: The oxidation state of osmium (Os) in OsO₄ is
a) +7
b) +6
c) +4
d) +8
Answer: c

Question: Oxidation number of carbon in CH₂Cl₂ is
a) –4
b) +4
c) 0
d) –2
Answer: c

Question: Oxidation state of Fe in Fe₃O₄ is
a) 5 4 
b) 4 5 
c) 3 2
d) 8 3 
Answer: d

Question: In which of the following compounds the oxidation number of carbon is not zero?
a) HCHO
b) CH₃COOH
c) C₁₂H₂₂O₁₁
d) CH3CHO
Answer: d

Question: In which of the following compounds, the oxidation number of iodine is fractional ?
a) IF₇
b) I⁻₃
c) IF₅
d) IF₃
Answer: b

Question: Reaction of sodium thiosulphate with iodine gives
a) tetrathionate ion 
b) sulphide ion
c) sulphate ion
d) sulphite ion. 
Answer: a

Question: Which of the following is the correct representative of stock notation for auric chloride?
a) Au(III)Cl₃
b) Au(II)Cl₂
c) Au(I)Cl₂
d) None of the options
Answer: a

Question: The correct order of N-compounds in its decreasing order of oxidation states is
a) HNO₃, NO, N₂, NH₄Cl
b) HNO₃, NO, NH4Cl, N₂
c) HNO₃, NH₄Cl, NO, N₂
d) NH₄Cl, N₂, NO, HNO₃
Answer: a

Question: The oxide, which cannot act as a reducing agent, is
a) NO₂
b) SO₂
c) CO₂
d) ClO₂
Answer: c

Question: The oxidation state of I in H₄IO^{6 –} is
a) + 1
b) – 1
c) + 7
d) + 5
Answer: c

Question: The oxidation number of chromium in potassium dichromate is
a) + 6
b) – 5
c) – 2
d) + 2
Answer: a

Question: Oxidation number of cobalt in K[Co(CO)₄] is
a) +1
b) +3
c) –1
d) –3
Answer: c

Question: The correct name for NO₂ using stock notation is
a) nitrogen dioxide
b) nitrogen (iv) oxide
c) nitrogen per oxide
d) All of these
Answer: b

Question: The loss of electron is termed as
a) oxidation
b) reduction
c) combustion
d) neutralization
Answer: a

Question: Among the following, identify the species with an atom in +6 oxidation state
a) MnO4–
b)Cr(CN)³⁻₆
c) NiF₆^{– 2}
d) CrO₂Cl₂
Answer: d

Question: When a strip of metallic zinc is placed in an aqueous solution of copper nitrate the blue colour of the solutiondisappear due to formation of
a) Cu²⁺
b) Zn²⁺
c) ZnS
d) Cus
Answer: b

Question: Co_(s) + Cu²⁺_(aq)→Co²⁺_(aq) + Cu_(s) The above reaction is
a) oxidation reaction
b) reduction reaction
c) redox reaction
d) None of the options
Answer: c

Question: A metal ion M³⁺ loses 3 electrons, its oxidation number will be
a) +3
b) +6
c) 0
d) –3
Answer: b

Question: In which of the following compounds oxygen has highest oxidation state and in which it has lowest oxidation state? OF₂, H₂O₂, KO₂, O₂F₂ 
a) Highest = KO₂, lowest = H₂O₂
b) Highest = OF₂, lowest = K₂O2
c) Highest = OF₂, lowest = KO₂
d) Highest = KO₂, lowest = H₂O₂
Answer: c

Question: What is the change in oxidation number of carbon in the following reaction? CH_4(g) + 4Cl_2(g) → CCl_4(l) + 4HCl_(g) 
a) + 4 to + 4
b) 0 to + 4
c) – 4 to + 4
d) 0 to – 4 
Answer: c

Question: The oxidation state of Cr in CrO₅ is
a) –6
b) +12
c) +6
d) +4
Answer: c

Question: ‘Oxidation number of H in NaH, CaH₂ and LiH, respectively is
a) +1, +1, –1
b) –1, +1, + 1
c) +1, + 1, + 1
d) –1,–1, –1
Answer: d

Question: Number of moles of MnO^{4 –} required to oxidize one mole of ferrous oxalate completely in acidic medium will be
a) 7.5 moles
b) 0.2 moles
c) 0.6 moles
d) 0.4 moles. 
Answer: d

Question: Which one of the following reaction involves oxidationreduction ?
a) H₂ +Br₂ →2HBr
b) NaBr + HCl → NaCl + HBr
c) HBr + AgNO ₃ → AgBr + HNO ₃
d) 2NaOH + H₂SO₄ → Na 2SO₄ + 2H₂O
Answer: a

Question: Which is the best description of the behaviour of bromine in the reaction given below? H₂O + Br₂ → HOBr + HBr
a) Proton acceptor only
b) Both oxidised and reduced
c) Oxidised only
d) Reduced only
Answer: b

Question: Oxidation numbers of P in PO₄^3–, of S in SO₄ ^2– and that of Cr in Cr₂O₇^2– are respectively
a) +3, +6 and +5
b) +5, +3 and +6
c) –3, +6 and +6
d) +5, +6 and +6
Answer: d

Question: Oxidation number of N in HNO₃ is
a) – 3.5
b) + 3.5
c) –5
d) + 5
Answer: d

Question: The oxidation states of sulphur in the anions SO3 2–, S2O4 2– and S2O6 2– follow the order
a) S₂O₄^2– < SO₃^2– < S₂O₆ ^2–
b) SO₃^2– < S₂O₄ ^2– < S₂O₆ ^2–
c) S₂O₄ ^2– < S₂O₆^2– < SO₃^2–
d) S₂O₆ ^2– < S₂O₄^2– < SO₃ ^2– 
Answer: a

Question: Without losing its concentration, ZnCl₂ solution cannot be kept in contact with
a) Pb
b) Al
c) Au
d) Ag 
Answer: b

Question: The pair of compounds that can exist together is
a) FeCl₃, SnCl₂
b) HgCl₂, SnCl₂
c) FeCl₂, SnCl₂
d) FeCl₃, KI 
Answer: c

Question: Oxidation number of nitrogen in (NH₄)2SO₄ is
a) –1/3
b) –1
c) +1
d) –3
Answer: d

Question: Which of the following process takes place in oxidation process?
a) Addition of oxygen
b) Addition of hydrogen
c) Removal of oxygen
d) Addition of chlorine
Answer: a

Question: In which of the following compounds, iron has lowest oxidation state?
a) K₃[Fe(CN)₆ ]
b) K₄[Fe(CN)₆ ]
c) FeSO₄.(NH₄ )2SO₄.6H₂O
d) Fe(CO)₅ 
Answer: d

Question: Which of the following is redox reaction?
a) Evaporation of H₂O
b) Both oxidation and reduction
c) H₂SO₄ with NaOH
d) In atmosphere O₃ from O₂ by lightning 
Answer: b

Question: The oxide, which cannot act as a reducing agent is
a) CO₂
b) ClO₂
c) NO₂
d) SO₂
Answer: a

Question: The oxidation number of sulphur in S₈, S₂F₂, H₂S respectively, are
a) 0, +1 and –2
b) +2, +1 and –2
c) 0, +1 and +2
d) –2, +1 and –2
Answer: a

Question: In which of the compounds does 'manganese' exhibit highest oxidation number ?
a) MnO₂
b) Mn3O₄
c) K2MnO₄
d) MnSO₄
Answer: c

Question: In which of the following reactions, there is no change in valency ?
a) 4 KClO₃→ 3KClO₄ + KCl
b) SO₂ + 2H₂S → 2H₂O + 3S
c) BaO₂ + H₂SO₄→ BaSO₄ + H₂O₂
d) 3 BaO + O₂ → 2 BaO₂.
Answer: c

Question: In reaction, 4Na + O₂ → 2Na₂O, sodium behaves as
a) oxidising agent
b) reducing agent
c) Both oxidising agent and reducing agent
d) None of the options
Answer: b

Question: Hot concentrated sulphuric acid is a moderately strong oxidizing agent. Which of the followingreactions does not show oxidizing behaviour?
a) Cu + 2H₂SO₄ → CuSO₄ + SO₂ + 2H₂O
b) S + 2H₂SO₄ → 3SO₂ + 2H₂O
c) C + 2H₂SO₄ → CO₂ + 2SO2 + 2H₂O
d) CaF2 + H₂SO₄ → CaSO₄ + 2HF
Answer: d

Question: The oxidation state of Fe in Fe₃O₄ is
a) + 3
b) 8/3
c) + 6
d) + 2
Answer: b

Question: One mole of N₂H₄ loses 10 moles of electrons to form a new compound, y. Assuming that all nitrogen appear in the newcompound, what is the oxidation state of nitrogen in y There is no change in the oxidation state of hydrogen )
a) –1
b) –3
c) +3
d) +5
Answer: c

 Question: The correct order of electron releasing tendency of the metals Cu, Zn and Ag is in the order:
a) Cu > Zn > Ag
b) Zn > Ag > Cu
c) Ag > Zn > Cu
d) Zn > Cu > Ag
Answer: d

 Question: (I) H₂O₂ + O₃→ H₂O + 2O₂ (II) H2O₂ + Ag₂O →2Ag + H₂O + O₂ Role of hydrogen peroxide in the above reactions is respectively
a) oxidizing in (I) and reducing in (II)
b) reducing in (I) and oxidizing in (II)
c) reducing in (I) and (II)
d) oxidizing in (I) and (II)
Answer: c